Fingernail in my eye.

First of all, ouch.: You may well have a corneal abrasion (scrape). These can be extremely painful and cause blurring and tearing, but usually heal on their own. It's safer to use an antibiotic while it heals, and there are some medications that can help with eye comfort as it heals. See an eye md (ophthalmologist) to find out exactly what to do.

Fingernail in eye.: If you mean a scratch to your eye via a fingernail, then treat as a corneal abrasion and use artificial tears and possibly and antibiotic ointment. If you mean truly a piece of fingernail in your eye (i have had a patient with a small piece of nail that flipped in her eye while clipping her nails at a salon, and she was treated for scratch by other doctors), you need to get it removed.

Corneal abrasion: Corneal abrasions can lead to infection and corneal scarring. The only way to diagnose an abrasion is to instill a dye such as flourescin and examination with either a coabalt blue lens or woods lamp. If pain persists you shoud be evaluated by an ophthalmologist.